In wireless communications between a base station and a User Equipment (UE), one TB that is capable of matching a channel and has a certain Modulation Coding Scheme (MCS), i.e., a certain spectral efficiency may be obtained in one transmission according to a channel situation between the base station and the UE. Therefore, cellular communication standards explicitly stipulate a set of MCS to match different radio channels. In practical communications, practical channel quality may be good. If the UE is in the center of a cell, the channel quality is higher than that needed by a maximum MCS in the standard. Under the existing MCS standard, when Signal to Noise Ratio (SNR) conditions of the UE in the cell are good or a transmitting power is redundant, the spectral efficiency may not reach optimum level due to the incapability of selecting a higher modulation scheme or making full use of the transmitting power. If the UE or the base station is allowed to transmit multiple TBs to the opposite party simultaneously, the spectral efficiency may be further improved without modifying an MCS standard definition. For example, if two TBs are superposed, an enough transmission power may be provided for the first TB, and a redundant power is allocated to the other TB, then the receiving party may separate the two TBs by using a Successive Interference Cancellation (SIC) technology.
The two TBs are transmitted over the same time-frequency resources, and during demodulation, the two TBs interfere with each other. In related communication technologies, two demodulation methods are provided. In the first method, each TB with interference from other TBs is demodulated. The implementation of the first method is simpler, but the performance is defective. In the second method, an SIC technology is used. Simple descriptions will be made by taking an interference cancellation process of two TBs as an example, and an interference cancellation process of multiple TBs is easy to be derived accordingly. In the interference cancellation process of two TBs, demodulation and decoding is firstly conducted to obtain information of TB1 (demodulating TB1 information with interference from TB2). Then, when TB2 information is demodulated, the TB1 information (which probably needs to be reconstructed) demodulated and decoded previously is subtracted from the TB2 information before the TB2 information is demodulated. Thus, the performance of the TB2 information may be greatly improved because of the cancellation of interference. Therefore, dual TBs may be received by using the SIC technology usually.
The two TBs are transmitted after being directly superposed. However, the finally-combined constellation points obtained in this direct superposition mode do not possess Gray mapping (adjacent mapped constellation points are different only in one bit, which makes optimal modulation performance) properties. FIG. 1 is a schematic diagram of a mode of directly superposing Quadrature Phase Shift Keying (QPSK) symbols and 16 Quadrature Amplitude Modulation (QAM) symbols in related communication technologies. As shown in FIG. 1, if a receiving end performs receiving by using an SIC, it may easily make mistakes to demodulate constellation points that do not possess Gray mapping properties. Although the SIC-based receiving may tolerate error propagation, the error propagation of a degree of 10% BLER cannot be omitted.
Therefore, the problem where constellation points finally combined by directly superposing two TBs do not possess Gray mapping properties exists in related communication technologies.